South Korea's newly elected president has described the security threat from North Korea as "grave".

Victorious in Wednesday's election, Park Geun-hye took 51.6 per cent of the vote to defeat her liberal rival, Moon Jae-in, and will be sworn in as South Korea's first female president in late February.

And if Pyongyang hoped the election might bring about a more conciliatory government in the South, after the hawkish attitude of the outgoing president, Lee Myung-bak, it will have been disappointed.

South Korea's president-elect Park Geun-hye (Reuters)

"This election was held in the middle of rapid changes in the situation surrounding the Korean Peninsula," Ms Park told reporters at the headquarters of the Saenuri Party.

"North Korea's long-range missile launch has symbolically showed the gravity of the security reality that we are faced with," she said.

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Identifying regional tensions and economic difficulties as the two most serious issues to contend with, Ms Park added that she believes the electorate had given her a mandate "to push wisely forward through these crises".

"I will keep my promise to the people that, without fail, I will open up a new era on the Korean Peninsula through strong national security and trust-based diplomacy," she said.

The then South Korean President Park Chung-hee, (right) and his daughter, Park Geun-hye, cast ballots in the election in 1977 in Seoul, South Korea (AP)

The election of Ms Park, the daughter of former dictator Park Chung-hee, has been welcomed in Washington, with President Barack Obama saying he looks forward to "working closely with" the incoming administration in Seoul.

Significantly, he emphasised that the alliance between the United States and South Korea "serves as a linchpin of peace and security in the Asia-Pacific region."

Ms Park will have personal reasons for wanting to keep North Korea in its place after a Japanese-born North Korean killed her mother, Yuk Young-soo, during an attempt on her father's life in August 1974.

For the remaining five years of President Park's regime, she acted as his first lady.

That does not mean that she rules out rapprochement with Pyongyang, however, and in the run-up to election day Park said she would seek opportunities to resume dialogue with the North and to resume the provision of humanitarian aid. Doing so will very much depend on the attitude of Pyongyang.

So far, there has been no comment on Ms Park's victory, although the state-run KCNA news agency ran an editorial timed to coincide with the election in the South that accused the Saenuri Party of "seriously defaming the dignity of the supreme leadership of the DPRK".

The report said the party's propaganda was "another unpardonable, hideous provocation against the DPRK".